1. Field of the Invention
This invention relates generally to liquid transfer systems and more particularly provides a pneumatically operated liquid transfer valve having a linearly movable valve element carrying segmenting passageway pairs of different volume so thaat at least two desired segments of a single sample can be obtained simultaneously in the absence of a two step segmentation heretofore characteristic of earlier transfer valves.
2. Description of the Prior Art
In the U.S. Pat. No. 3,549,994, there was provided a structure in which a sample of blood is drawn into a fluid system in which it is accurately diluted with a suitable diluent and divided into two samples for red and white blood cell determination. The red sample for red cell determination is counted and sized utilizing a COULTER scanning device and is discharged, while at the same time the other is lysed to break up the red cells and subjected to another COULTER electronic scanning device for a white cell count with the simultaneous examination of the sample for hemoglobin determination and discharge. The trademark COULTER is a registered trademark, Registration No. 995,825, owned by Coulter Electronics, Inc. of Hialeah, Florida, U.S.A.
Processing is automatic and continuous for samples drawn into the apparatus at intervals exceeding at least a certain minimum time duration. The structure therein disclosed included means for combining the data automatically to ascertain certain of the parameters which are susceptible of derivation from determinations made, and producing data corresponding to all of the parameters both determined and derived from the apparatus. These parameters were blood counts, sizes, percentages, and the like, accepted in the medical arts as aids for diagnosis, treatment, and research. The structure therein disclosed utilized vessels, valves, and connecting conduits for the intermixing and/or diluting of fluids primarily for the purpose of making measurements and tests on such fluids. Of course, it should be appreciated that such description is somewhat general and while primarily utilized with an automatic instrument such as disclosed in the above-identified patent which employs the electronic particle analyzing apparatus operating upon principles disclosed in U.S. Pat. No. 2,656,508, it is capable of many uses. In medicine, biology, chemistry, and allied fields, research as well as routine testing required the use of apparatus which can produce fluid mixtures of specific concentrations accurately and automatically and particularly, can feed known quantities of fluids to a selected ones of a plurality of locations.
In the apparatus referred to in U.S. Pat. No. 3,549,994, samples of whole blood were introduced one every 15 seconds. The apparatus performs the requisite dilutions, tests, and computations needed for obtaining blood counts of white and red cells, a hematocrit determination, a hemoglobin measurement, and so on. Accordingly, such automatic instrument is required quickly and accurately to prepare the necessary sample suspensions of predetermined concentration for transfer to the testing apparatus of the instrument. Liquids must be pumped, transferred and moved between vessel and it is with such type of liquid transfer apparatus that this invention is concerned.
One type of the liquid transfer valve structure has been disclosed in U.S. Pat. No. 3,567,390 and that particularly consisted of a central element and a pair of outer elements engaged against opposite faces of the central element to sandwich same therebetween. The central element is movable relative to the other element between first and second positions. At least one measuring conduit is formed in the central element and at least a pair of ports are provided in each outer element. Each of the ports in one of the outer elements aligns with a port carried by other outer element so that two fluid paths are defined. The central member is indexed to a first position to align one measuring conduit with one of said fluid paths for reception in that one conduit of a portion of the fluid sample. The central element then is moved to a second position. By virtue of such movement, the volume of the sample in the measuring conduit is segmented and deposited in the other fluid path for combining with a diluent introduced therein so as to provide a precise dilution.
In the various fluid transfer valve constructions disclosed in the aforesaid patents, the movable element is either pivoted or rotated or both to effect the segmenting of the precise volume quantities of sample. Further, in some of said earlier valve constructions a second or companion segmenting passageway is provided. Immediately subsequent to the delivery of the first sample for the first testing apparatus forming the first dilution, the first step of the second dilution is effected by drawing to the companion segmenting passageway, a precise volume of said first dilution, thereafter actuating the valve to deliver a precise volume of first dilution to a second testing apparatus along with a predetermined volume of diluent thereby to effect a second dilution. The first dilution is utilized for the purpose of making white blood cell evaluations as well as hematocrit through the process of lysing the red blood cells from the sample. The second dilution is utilized to evaluate the red blood cells, for example, which requires a substantially more dilute sample. It would be advantageous and of course more efficient, simultaneously to direct the proper dilutions to testing apparatus so that both operations, that is the white blood cell determinations and the red blood cell determinations can be carried out substantially simultaneously on the same sample. The previously available liquid transfer valve means for effecting the double dilutions contemplate a seriatum operation where for each sample the white blood cell evaluation is determined and thereafter the red blood cell evaluation is determined.
In addition, the fluid transfer valve constructions heretofore referred to include associated therewith plural drive components and elements that require maintenance of very close tolerances in the course of manufacture. Failure to meet those close tolerances would result in either inaccurate alignment, movement and the like effecting the accurate measuring and transfer of the liquid. Relatively complex means was required to cleanse and to drain the valve passageways so that successive samples were not contaminated. Difficulties in loading as well as dispensing provide the impetus for improvement. Simplification of the heretofore known valve structures so as to perhaps reduce the cost yet maintain the necessary accuracy is a continuing problem.
Accordingly, a fluid transfer valve is sought which can effect at least two different degrees of dilution from a single sample simultaneously and with conservation of sample and diluent.
It has been increasingly common to obtain relatively small whole blood samples using micropipettes sometimes referred to a finger-sticks. Separate valving and feeds were required to perform the desired analysis of such samples since the volume of sample involved is small. Ordinarily, the finger-stick was introduced to a precise volume of diluent in a separate vessel. A small fraction was taken for further dilution while the remainder was treated for other analyses and introduced to other testing apparatus.
A need thus arises for a fluid transfer valve which can allow the operator to choose between segmenting operation on a whole blood sample or a prediluted sample without using separate valving, considerable increase in fluid lines, etc.
Attention should be directed also to the need to provice a separate vessel in at least one testing apparatus, that is, for white blood cell determinations so that the first dilution could be made without lysing since a portion thereof would have to be used to make the second dilution. The advantages of providing a valve where the original blood sample could be utilized to provide both dilutions are evident, with particular advantage gain in permitting lysing and the mixing to take place in a single vessel which can be the bath in which the testing is performed.